Hermann Kaindl

Requirements Engineering and Technology Transfer: Obstacles, Incentives and Improvement Agenda

For many years, research results in requirements engineering (RE) have been developed without much interaction with, or impact on, industrial practice. Why is it so difficult to introduce RE research results into mainstream RE practice? This paper attempts to provide answers to this question by describing obstacles that researchers and practitioners have encountered when they attempted technology transfer. In addition, major incentives for using RE methods are discussed, along with ideas for improving current RE practice. The paper summarises, clarifies and extends the results of two panel discussions, one at the Twelfth Conference on Advanced information Systems Engineering (CAiSE’00) and the other at the Fourth IEEE Conference on Requirements Engineering (ICRE’00).

The missing link in requirements engineering

Especially the early phase of requirements engineering is one of the most important and least supported parts of the software life cycle. Since pure natural language has its disadvantages, and directly arriving at a formal representation is very difficult, a link through a mediating representation is missing. We use hypertext for this purpose, providing also links among requirements statements and the representation of objects in a domain model. This possibility of explicit representation of links allows the users and analysts to make relationships and dependencies explicit and helps to be aware of them. Actually, our approach and the tool supporting it use a combination of various technologies, including also object-oriented approaches and a grain of artificial intelligence (in particular frames). Therefore, inheritance is provided by our tool already in the early phase of requirements engineering. In particular, we found it very useful to view requirements as objects. A key idea is to support the ordering of ideas especially through classification already in the early stages. While our approach is not intended to substitute useful existing techniques emphasizing more formal representations, it can be combined with them.

Bidirectional heuristic search reconsidered

The assessment of bidirectional heuristic search has been incorrect since it was first published more than a quarter of a century ago. For quite a long time, this search strategy did not achieve the expected results, and there was a major misunderstanding about the reasons behind it. Although there is still wide-spread belief that bidirectional heuristic search is afflicted by the problem of search frontiers passing each other, we demonstrate that this conjecture is wrong. Based on this finding, we present both a new generic approach to bidirectional heuristic search and a new approach to dynamically improving heuristic values that is feasible in bidirectional search only. These approaches are put into perspective with both the traditional and more recently proposed approaches in order to facilitate a better overall understanding. Empirical results of experiments with our new approaches show that bidirectional heuristic search can be performed very efficiently and also with limited memory. These results suggest that bidirectional heuristic search appears to be better for solving certain difficult problems than corresponding unidirectional search. This provides some evidence for the usefulness of a search strategy that was long neglected. In summary, we show that bidirectional heuristic search is viable and consequently propose that it be reconsidered.

A design process based on a model combining scenarios with goals and functions

While promising approaches to early system design using scenarios have been proposed, no design process is available that guides scenario-based design. We present a model that combines scenarios both with functions and goals. Functions are required to make the desired behavior of some scenario happen in order to achieve one or more goals. Using this model, we propose a systematic and concrete design process that is both model-driven and data-driven. Our design process supports the transition from the current to a new system and guides the design of a new system. In addition, this process makes it possible to detect a certain kind of redundancy and to improve both completeness and understandability of the resulting design. We have applied our approach in real-world projects, and our experience suggests the utility of this approach.

Difficulties in the transition from OO analysis to design

The transition from object-oriented (OO) analysis to OO design is indeed difficult. Unfortunately, most of the literature on this topic has incorrectly assessed this issue since the notion of OO analysis was introduced about a decade ago.

Reusing single system requirements from application family requirements

Reuse and requirements engineering are very important for efficient and successful systems development. However there are many open issues for performing them well in practice, especially raise of requirements. We present a new approach to reusing requirements based on application families i.e. several systems in a given problem domain. In contrast to precious approaches, an application family model in our approach consists of a pool of requirements (linked in a lattice structure), a domain model and a set of discriminants (a special kind of requirement that differentiate one system from another). We focus on how to make an efficient and clean selection of the requirements for a new system from an application family model. We have developed a method for solving this problem and a prototypical tool for supporting it. The method and the prototype were successfully developed under a study contract for ESA (European Space Agency). We present a case study, where we generated commanding requirements for an individual mission from an application family model of commanding requirements for spacecraft control operating systems. As a consequence, we propose this approach for reusing requirements based an application families.

A practical approach to combining requirements definition and object-oriented analysis

According to our experience in real‐world projects, we still observe deficiencies of current methods for object‐oriented analysis (OOA), especially in respect to the early elicitation and definition of requirements. Therefore, we used object‐oriented technology and hypertext to develop a practical approach – with tool support – that tightly combines OOA with requirements definition. This novel approach is compatible with virtually any OOA method. While more work needs to be done especially for supporting the process of requirements definition, the observed deficiencies and current limitations of existing OOA methods are addressed and partly removed through this combination. We have applied our approach in real‐world projects, and our experience suggests the usefulness of this approach. Essentially, its use leads to a more complete and structured definition of the requirements, and consequently we derive some recommendations for practitioners.

A discourse model for interaction design based on theories of human communication

Most current models of interaction design build on scenarios and task analysis. We think that interaction design should be more along the lines of communication between humans. With this motivation, our paper presents a new approach to modeling interaction design based on insights from theories of human communication. From such discourse models, we aim for automated generation of user interfaces.

Minimax search algorithms with and without aspiration windows

Investigation of several algorithms for computing exact minimax values of game trees (utilizing backward pruning) are discussed. The focus is on trees with an ordering similar to that actually found in game playing practice. The authors compare the algorithms using two different distributions of the static values, the uniform distribution and a distribution estimated from practical data. A systematic comparison of using aspiration windows for all of the usual minimax algorithms is presented. The effects of aspiration windows of varying size and position are analyzed. Increasing the ordering of moves to near the optimum results in unexpectedly high savings. Algorithms with linear space complexity benefit most. Although the ordering of the first move is of predominant importance, that of the remainder has only second-order effects. The use of an aspiration window not only makes alpha-beta search competitive, but there also exist dependencies of its effects on certain properties of the trees. >

Coupling and cohesion metrics for knowledge-based systems using frames and rules

Software systems and in particular also knowledge-based systems (KBS) become increasingly large and complex. In response to this challenge, software engineering has a long tradition of advocating modularity. This has also heavily influenced object-oriented development. For measuring certain important aspects of modularity, coupling and cohesion metrics have been developed. Metrics have also attracted considerable attention for object-oriented development. For KBS development, however, no such metrics are available yet. This article presents the core of the first metrics suite for KBS development, its coupling and cohesion metrics. These metrics measure modularity in terms of the relations induced between slots of frames through their common references in rules. We show the soundness of these metrics according to theory and report on their usefulness in practice. As a consequence, we propose using our metrics in order to improve KBS development, and developing other important metrics and assessing their theoretical soundness along these lines.